Automatic belt tensioning devices are frequently subjected to harsh operating environments that include contaminants such as mud, salt, dust, water, etc. At times the contaminants can be forced into the tensioner with power-washing or some other concentrated spray. At other times contaminants may enter the tensioner as a result of immersion. Even during normal operating conditions, however, contaminants may work their way into the tensioner. Contaminants that become trapped in a tensioner, especially contaminants suspended in a liquid solution such as mud, may increase the potential for wear, corrosion, spring break, high damping and/or lockup.
Previous attempts have been made to open up the tensioner body to allow contaminants both in and out of the tensioner. However, many of these attempts have resulted in increases in wear, spring break, high damping and/or lockup. Additionally, many of these prior art designs do not provide for additional spring bushing area, additional casting strength, etc.
Another approach is to better protect the tensioner body through improved sealing. Known sealing techniques have done a good job of precluding large contaminants. The task now, however, is to also provide an effective way to prevent the entrance of, and at the same time permit the exit of, smaller contaminants. Attempts have been made to place drains in the outwardly facing lateral sides of the tensioner spring case. The problem, however, is that these drains also permit contaminants back into the tensioner through the same hole.
Accordingly, an improved tensioner design is desired that provides effective drainage without compromising the likelihood of contaminant entry.